Digital twin-based synchronous 4D BIM-driven UAS mission planning using the combined graph approach

Existing Unmanned Aerial Systems (UAS) mission planning approaches for construction monitoring, either rescan the entire building structure or address isolated coverage problems and rely on single-source inputs. This study introduces a mission-planning approach and establishes a framework that (i) prioritizes multi-type inspection fronts (specific indoor spaces/elements, facade regions, topmost in-progress levels), (ii) systematically fuses multi-source project information—into a digital twin-based synchronous 4D Building Information Model (BIM) by emerging an as-planned 4D BIM (with the latest schedule updates) and a digitally twinned as-built 4D BIM computed from a centralized point cloud repository—and (iii) employs a combined graph (topology-based model graph overlaid with a user-defined network grid) to improve reachability in complex interiors. This framework transcends traditional 4D BIM by establishing an asynchronous digital twin of the evolving construction project—that synchronizes the physical site and its digital counterpart after each mission scheduled on a user-defined time interval. Each completed mission updates the as-built 4D BIM, which regenerates the synchronous model for subsequent mission planning, thus maintaining a live, feedback-driven digital representation of the construction process. Validation was conducted in a virtual simulator using hypothetical building use cases of increasing architectural complexity, where the combined graph approach was compared against model-only graphs. Results demonstrated improved scan-point accessibility and reduced mission path length across all use cases. In addition, a comparative analysis of grid patterns showed that triangular, brace, and 3D Voronoi lattices provided the highest efficiency under concave and non-orthogonal conditions.